Is Helicobacter pylori always a "bad guy"?

Various clinical presentations have been ascribed to Helicobacter (H.) pylori. Most importantly, H. pylori is considered the leading cause of gastric cancer worldwide and because of that, in adult population, it is listed as a number one carcinogen. However, children are less prone to develop H. pylori related serious diseases such as peptic ulcer disease (PUD) and cases of malignancy are only sporadically reported. On the other hand, there is an increasing level of evidence suggesting that H. pylori in children could also have a beneficial effect. Recently, several data confirmed previously described inverse relationship of H. pylori infection and gastroesophageal reflux disease. Furthermore, it has been hypothesized that an increased prevalence of allergic diseases could be, at least partially, explained by the decreased incidence of H. pylori infection. H. pylori can, to some degree, influence immunological response. It has an ability to promote high proinflammatory cytokine expression in the gastric mucosa shifting immunity towards Th1 response, which could be a plausible explanation for the down-regulated clinical expression of allergies (including asthma) in patients with H. pylori gastritis. Based on these findings the aim of this review is to present "pros and cons" for H. pylori eradication in children.